Novolak-ABS binder for a grinding wheel

ABSTRACT

An acrylonitrile-butadiene-styrene terpolymer is added to a phenol formaldehyde novolak to form a grinding wheel binder imparting increased flexural strength to the grinding wheel.

This is a division of application Ser. No. 430,539 filed Jan. 3, 1974.

The present invention relates to grinding wheels having improved novolak resin binders.

Phenol-formaldehyde novolak resins as is well known in the art are permanently thermoplastic or fusible resins prepared by condensing phenol with formaldehyde under acid conditions using about 0.5 to 1.0 moles, generally about 0.7 to 0.9 moles, of formaldehyde per mole of phenol. The resins are converted to the infusible condition by adding sufficient hexamethylenetetramine for this purpose. Such phenol-formaldehyde novolaks admixed with hexamethylenetetramine are well known as binders for abrasives, more specifically for abrasive grinding wheels.

It has now been found that the flexural strength of grinding wheels containing phenol-formaldehyde novolak resin binders can be improved by incorporating an acrylonitrile-butadiene-styrene (ABS) terpolymer into the novolak. Desirably, the ABS terpolymer is added during the manufacture of the resin. The most desirable time to add the ABS terpolymer is before the novolak is formed. Thus, the ABS terpolymer can be added during distillation, after distillation, after obtaining free formaldehyde or to the phenol before the formaldehyde is added. The latter procedure is preferred. The amount of ABS terpolymer is normally 1 to 30% based on the weight of phenol, preferably between 5 and 20%. In fact, up to 50% of the ABS terpolymer based on the weight of the phenol can be employed with some impairment of properties.

The amount of hexamethylenetetramine is not critical and can be that usually employed to cure novolak resins. Thus, there is normally employed 4.6 to 13.7% hexamethylenetetramine, preferably 6.4 to 11.9%, based on the weight of the novolak. In place of hexamethylenetetramine there can be used other conventional hardening agents for novolaks, e.g., paraformaldehydes.

Any of the conventional acids and acidic materials employed to prepare novolak resins can be employed as catalysts, e.g., sulfuric acid, oxalic acid, maleic anhydride, sulfamic acid, phenolsulfonic acid, diethyl sulfate, toluenesulfonic acid (usually employed as the commercial mixture of isomers known as TX acid) and phosphoric acid.

Any conventional abrasive grains can be employed to form the wheel. Thus, there can be used for example fused aluminum oxide, silicon carbide, diamonds, fused zirconia, sintered alumina, etc.

There can be employed commercially available ABS terpolymers, e.g., Dow 500 and Dow 300. Other suitable ABS terpolymers are those identified below as ABSON 820X13, ABSON 820X14, ABSON 820X15 and ABSON 820X16. ABSON 820X14 has a nitrogen content of 6.6% and the other ABSON terpolymers are of somewhat lower nitrogen content. Other properties of the ABSON terpolymers which are available as powders are set forth below.

    ______________________________________                                         ABSON ABS TERPOLYMER RESIN PROPERTIES                                                         820X13                                                                               820X14  820X15  820X16                                    ______________________________________                                         Tensile Strength (psi)                                                                          2,900   6,200   5,500 5,800                                   Ultimate Elongation (%)                                                                         200     15      3     3                                       Izod Impact Strength                                                           at R.T.          1.7     1.8     7.5   6.5                                     -20° F.   1.3     1.4     2.9   1.2                                     -40° F.   1.2     0.8     1.9   0.8                                     Hardness, Rockwell R                                                                            70      116     103   106                                     Hardness, Shore D                                                                               66      --      75    73                                      Heat Deflection Temp.                                                          264 psi (° F.)                                                                           181     203     198   196                                     Specific Gravity 0.99    1.06    1.04  1.04                                    Viscosity, Poises × 10.sup.3                                             Instron Rheometer (225° C)                                              437° F.                                                                 at 1000 sec.sup.-1                                                                              6.7     3.1     3.4   3.0                                     100 sec.sup.-1   42      15      15    11                                      10 sec.sup.-1    270     53      40    23                                      1 sec.sup.-1     930     110     80    40                                      Solution Viscosity (Cps)*                                                      Brookfield at 20 RPM                                                           10% T.S. in THF, Initial                                                                        640     --      38    --                                      1 day            640     --      42    --                                      30 days          584     --      50    --                                      10% T.S. in MEK, Initial                                                                        9       --      10.5  --                                      1 day            9       --      11.5  --                                      30 days          8.5     --      10.0  --                                      ______________________________________                                          *Values normalized with correction factors for various size spindles.    

Unless otherwise indicated all parts and percentages are by weight.

EXAMPLE I

A. c. p. phenol -- 2000 Parts

B. oxalic Acid -- 20 Parts

C. abson 820X16 -- 20 Parts

D. 37% formalin -- 1294 Parts

E. 28% ammonia -- 10.4 Parts

Components "A" through "C" were loaded into a reaction vessel set for reflux. The components were heated to atmospheric reflux (100° C.). Component "D" was added dropwise, at reflux, to the reaction vessel over a 30-60 minute period. Enough heat was added to maintain a reflux. After all of component "D" was added, the batch was held at reflux (100° C.) until the free formaldehyde in the refluxate was less than one percent. At this point, component "E" was added to the reaction vessel and the resulting material was distilled to a grindable resin.

Ball and ring softening point = 100° C.

Yield = 1240 Parts

EXAMPLE II:

A. c. p. phenol -- 2000 Parts

B. oxalic Acid -- 20 Parts

C. abson 820X16 -- 100 Parts

D. 37% formalin -- 1294 Parts

E. 28% ammonia -- 10.4 Parts

The reaction procedure was the same as in Example I.

Ball and ring softening point = 104° C. (ASTM E 28-67)

Yield = 2160 Parts

EXAMPLE III:

A. c. p. phenol -- 2000 Parts

B. oxalic Acid -- 20 Parts

C. abson 820X16 -- 200 Parts

D. 37% formalin -- 1294 Parts

E. 28% ammonia -- 10.4 Parts

The reaction procedure was the same as in Example I.

Ball and ring softening point = 106° C.

Yield = 2260 Parts

EXAMPLE IV:

A. c. p. phenol -- 2000 Parts

B. oxalic Acid -- 20 Parts

C. abson 820X16 -- 400 Parts

D. 37% formalin -- 1294 Parts

E. 28% ammonia -- 10.4 Parts

The reaction procedure was the same as in Example I.

Ball and ring softening point = 113° C.

Yield = 2520 Parts

EXAMPLE V:

    ______________________________________                                         A. C.P. Phenol       2000 Parts                                                B. Oxalic Acid       20 Parts                                                  C. Abson 820X16      600 Parts                                                 D. 37% Formalin      1294 Parts                                                E. 28% Ammonia       10.4 Parts                                                ______________________________________                                    

The reaction procedure was the same as in Example I.

Ball and ring softening point = 117° C.

Yield = 2635 parts

EXAMPLE VI:

    ______________________________________                                         A. C.P. Phenol       2000 Parts                                                B. Oxalic Acid       20 Parts                                                  C. Abson 820X16      1000 Parts                                                D. 37% Formalin      1294 Parts                                                E. 28% Ammonia       10.4 Parts                                                ______________________________________                                    

The reaction procedure was the same as in Example I.

Ball and ring softening point = 118° C.

Yield = 3025 Parts

EXAMPLE VII:

Each of the products of Examples I through VI were ground with hexamethylenetetramine. The following formula was used to determine the ratio of hexamethylenetetramine to resin: ##EQU1##

    ______________________________________                                         Resin    Parts hexamethylenetetramine/1000 parts resin                         ______________________________________                                         Example I                                                                               89                                                                    Example II                                                                              86                                                                    Example III                                                                             82                                                                    Example IV                                                                              76                                                                    Example V                                                                               69                                                                    Example VI                                                                              60                                                                    ______________________________________                                    

EXAMPLE VIII:

The products of Examples I through VI (ground with hexamethylenetetramine as set forth in Example VII) were evaluated in grinding wheel test bars according to the following formula:

    ______________________________________                                                                   PARTS                                                ______________________________________                                         A. Number 60 grit (Aluminum oxide, regular alundum)                                                        1625                                               B. SG 3513 (wetting resin, specifically an ammonia                             catalyzed phenol-formaldehyde resole)                                                                       35.6                                              C. Grinding Wheel binder (Examples I through VI                                ground with hexamethylenetetramine as set forth                                                            142.5                                              in Example VII)                                                                ______________________________________                                    

The grit was added to a Hobart mixer and the SG-3513 was then added to the grit. The mixer was turned on for two minutes or until the grit was fully wetted. The binder resin was then added to the grit SG-3513 mixture and mixed for two minutes, then 323 grams of the resulting wet mix was distributed evenly into a stainless steel mold. The mixture was then pressed into a 1 inch × 1 inch × 8 inch bar on a Watson Stillman hydraulic press. The pressed bars were cured as follows:

1. 14 hours starting at ambient temperatures and to 350° F.

2. 14 hours at 350° F.

3. 12 hours going from 350° F. to ambient temperatures.

The resulting flexural bars were then broken on an Instron tester using a 6 inch span. Four bars were fabricated for each test. This will hold for all the data cited throughout this paper.

    ______________________________________                                         Flexural Strengths (PSI)                                                                Room               Room Temperature after                             Example  Temperature                                                                             300° C.                                                                           10-Day Water Soak                                  ______________________________________                                         i      5040       1134      2277                                               II     4941       1350      2187                                               III    6030       1332      2115                                               IV     4590       1394      1602                                               V      4212       1134      2502                                               VI     3717        837      2142                                               *SG-3350                                                                              4900       1000      3200                                               *SG-3130                                                                              3900       1700      2400                                               ______________________________________                                          *SG-3130 is a commercial phenol-formaldehyde novolak (phenol to                formaldehyde 1:0.78)                                                           *SG-3350 is a commercial phenol-formaldehyde resin containing 10% Hycar        (butadiene-acrylonitrile copolymer).                                           The values for SG-3130 and SG-3350 are typical values.                   

EXAMPLE IX:

The resin in Example III was ground with various levels of hexamethylenetetramine.

    ______________________________________                                         No.     Parts Resin                                                                               Parts hexamethylenetetramine                                ______________________________________                                         1       1000        46                                                         2       1000        64                                                         3       1000        82                                                         4       1000       100                                                         5       1000       119                                                         6       1000       137                                                         ______________________________________                                    

These resins were then tested according to the procedures outlined in Example VIII.

    ______________________________________                                         Flexural Strengths (PSI)                                                                                   Room Temperature after                             No.  Room Temperature                                                                              300° C.                                                                         10-Day Water Soak                                  ______________________________________                                         1    4950            540    1530                                               2    5562            657    2277                                               3    6003           1332    4392                                               4    5517           1917    3853                                               5    4905           2007    3375                                               6    4500           2430    3015                                               ______________________________________                                    

EXAMPLE X:

Various catalysts were tried using the resin formulation of Example III and substituting the following catalyst loads.

    ______________________________________                                         No.  Catalyst        Parts Catalyst/1000 Parts Phenol                          ______________________________________                                         1    Oxalic Acid     20                                                        2    Maleic Anhydride                                                                               10                                                        3    85% Phosphoric Acid                                                                            25                                                        4    Sulfamic Acid   25                                                        5    Con. Hydrochloric Acid                                                                         5                                                         6    Diethyl sulfate 7.5                                                       7    Phenolsulfonic Acid                                                                            6                                                         8    TX Acid         6                                                         9    Con. Sulfuric Acid                                                                             2                                                         ______________________________________                                    

These resins were ground with 82 parts of hexamethylenetetramine per 1000 parts resin and then tested according to the procedures outlined in Example VIII.

    ______________________________________                                         Flexural Strengths (PSI)                                                                                   Room Temperature After                             No.  Room Temperature                                                                              300° C.                                                                         10-Day Water Soak                                  ______________________________________                                         1    5607           1080    1827                                               2    4995           1017    1557                                               3    3447           1062     832                                               4    5887           1125    2493                                               5    5670           1062    2970                                               6    5112            765    2970                                               7    6309            720    3087                                               8    5860            945    2520                                               9    5300           1665    4050                                               ______________________________________                                    

EXAMPLE XI:

In this example the formaldehyde/phenol mole ratio was varied while the ABS load remained constant at ten percent based on the phenol load. The procedure, materials and load outlined in Example III were used varying only the formaldehyde load.

    ______________________________________                                                                 Ball and Ring                                                                  Softening Point                                        No.        F/P mole ratio                                                                              ° C.                                            ______________________________________                                         1          0.69         103                                                    2          0.71         100                                                    3          0.73         102                                                    4          0.75         106                                                    5          0.77         108                                                    6          0.79         112                                                    7          0.81         117                                                    8          0.83         112                                                    ______________________________________                                    

These resins were ground with 82 parts hexamethylene-tetramine per 1000 parts resin and then tested according to the procedures outlined in Example VIII.

    ______________________________________                                         Flexural Strengths (PSI)                                                                                   Room Temperature After                             No.  Room Temperature                                                                              300° C.                                                                         10-Day Water Soak                                  ______________________________________                                         1    6020           1692    2502                                               2    6075           1935    2547                                               3    4995           2547    1872                                               4    6075           1377    2610                                               5    4860           1845    1800                                               6    4617           1575    1575                                               7    5391           1377    2187                                               8    4725           1800    1557                                               ______________________________________                                    

EXAMPLE XII:

In this example various ABS resins were utilized at weight for weight substitution in the formulation outlined in Example III.

    ______________________________________                                                                          Ball and Ring                                                                  Softening Point                               No.  ABS Used  Manufacturer      ° C                                    ______________________________________                                         1    820X13    B.F. Goodrich Chemical Co.                                                                       111                                           2    820X14    B.F. Goodrich Chemical Co.                                                                       109                                           3    820X15    B.F. Goodrich Chemical Co.                                                                       114                                           4    820X16    B.F. Goodrich Chemical Co.                                                                       103                                           5    Dow 500   Dow Chemical Co.  105                                           6    Dow 300   Dow Chemical Co.  107                                           ______________________________________                                    

These resins were ground with 82 parts hexamethylenetetramine per 1000 parts resin and then tested according to the procedures outlined in Example VIII. No. 4 had the best properties and No. 1 the second best properties.

    ______________________________________                                         No.      Room Temperature Flexural Strengths (PSI)                             ______________________________________                                         1        5980                                                                  2        5152                                                                  3        5328                                                                  4        6120                                                                  5        3978                                                                  6        4563                                                                  ______________________________________                                    

EXAMPLE XIII:

    ______________________________________                                         A. C.P. Phenol       2000 Parts                                                B. Oxalic Acid       20 Parts                                                  C. 37% Formalin      1294 Parts                                                D. Abson 820X16      200 Parts                                                 E. 28% Ammonia       10.4 Parts                                                ______________________________________                                    

Materials "A" and "B" were loaded into a reaction vessel set up for atmospheric reflux and heated to 100° C. Material "C" was added at 100° C. over a 30 to 60 minute period. The reaction mixture was then held at 100° C. (atmospheric reflux) until the free formaldehyde level of the refluxate was less than one percent. Materials "D" and "E" were added and the resulting resin was distilled to a grindable resin.

Ball and ring softening point = 111° C.

EXAMPLE XIV

Load: Same as Example XIII.

Materials "A" and "B" were loaded into a reaction vessel set up for atmospheric reflux and heated to 100° C. Material "C" was added at 100° C. over a 30 to 60 minute period. The reaction mixture was then held at 100° C. (atmospheric reflux) until the free formaldehyde level of the refluxate was one percent or less. Material "E" was added. The resulting resin was distilled atmospherically to 130° C. Material "D" was added and the resin was then distilled to a grindable resin.

Ball and ring softening point = 108° C.

EXAMPLE XV:

Load: The same as Example XIII.

Materials "A" and "B" were loaded into a reaction vessel set up for atmospheric reflux and heated to 100° C. Material "C" was added at 100° C. over a 30 to 60 minutes period. The reaction mixture was then held at 100° C. until the free formaldehyde in the refluxate was less than one percent. Material "E" was added. The batch was then distilled to a grindable resin. Material "D" was then added and mixed in.

Ball and ring softening point = 111° C.

EXAMPLE XVI:

    ______________________________________                                         A. C.P. Phenol       2000 Parts                                                B. Oxalic Acid       20 Parts                                                  C. 37% Formalin      1294 Parts                                                D. 28% Ammonia       10.4 Parts                                                ______________________________________                                    

Materials "A" and "B" were added to a reaction vessel set for atmospheric reflux and heated to 100° C. Material "C" was added at 100° C. over a 30 to 60 minute period. The reaction mixture was held at 100° C. until the free formaldehyde in the refluxate was less than one percent. Material "D" was added and the resin was distilled to a grindable resin.

Ball and ring softening point = 102° C.

EXAMPLE XVII:

The resins from Examples III, XIII, XIV, XV, and XVI were ground with 82 parts hexamethylenetetramine per 1000 parts resin.

Flexural bars were prepared from the powdered resins in Examples III, XIII, XIV, and XV using the procedures outlined in Example VIII. Flexural bars were also prepared from the powdered resin in Example XVI using two minor modifications of the procedure outlined in Example VIII.

XVI-A, 10 parts Abson 820X16 per 100 parts powdered resin were blended during the grind. The resulting mixture was utilized as part "C" in the test procedure outlined in Example VIII.

XVI-B, 10 parts Abson 820X16 per 100 parts resin was added to the formulation described in Example VIII.

    ______________________________________                                         Example    Room Temperature Flexural Strengths (PSI)                           ______________________________________                                         III        6030                                                                XIII       5373                                                                XIV        5220                                                                XV         4707                                                                XVI-A      3897                                                                XVI-B      3555                                                                ______________________________________                                    

EXAMPLE XVIII:

    ______________________________________                                         A. C.P. Phenol       1000 Parts                                                B. Oxalic Acid       20 Parts                                                  C. Abson 820X16      100 Parts                                                 D. 37% Formaldehyde  647 Parts                                                 ______________________________________                                    

The phenol and oxalic acid were added to the reaction vessel along with the ABS and melt blended at elevated temperatures. When the melt blend has been completed the formaldehyde is added dropwise and taken to a final free formaldehyde of zero percent. The resulting condensate is distilled to a grindable resin, ground with hexamethylenetetramine and utilized as a grinding wheel binder.

Listed below are the results on an ABS modified grinding wheel binder along with the results on a general purpose resin (SG-3130) and two high performance novolak resins, SG-3350 (Hycar modified) and SG-3378 (epoxy modified). The water soak samples were immersed for ten days prior to flexural strength determination.

    ______________________________________                                         Flexural Strength (PSI)                                                                  Room               Room Temperature After                            Resin (#) Temperature                                                                               300° C.                                                                         Water Soak                                        ______________________________________                                         Example XVIII                                                                            6120       1710    3573                                              3350 (Hycar)                                                                             4734       1197    2457                                              3130      3690       1755    2205                                              3378      3780       1845    1440                                              ______________________________________                                          Resin 3378 had 15% of Epon 1007 (bisphenol A-epichlorohydrin resin Mol.        Wt. 2000-2500) as a modifier to the novolak.                              

What is claimed is:
 1. A process of preparing a composition suitable for bonding abrasive grits comprising forming a novolak from phenol and formaldehyde in the presence of an acid catalyst and adding an acrylonitrile-butadiene-styrene terpolymer resin in an amount of 1 to 30% of the phenol prior to the completion of the formation of the novolak.
 2. A process according to claim 1 including the step of adding a hardening agent for the novolak after formation of the novolak, said hardening agent being present in an amount sufficient to harden the novolak upon subsequent heating.
 3. The product prepared by the process of claim
 2. 4. The product prepared by the process of claim
 1. 5. A process according to claim 1 wherein there is added 5 to 20% of ABS resin based on the phenol prior to the completion of the formulation of the novolak.
 6. The product prepared by the process of claim
 5. 